Those answers are due by 7th June, or next Wednesday. A representative for the IRS was not immediately available to comment when contacted about its plans to respond.

Notably, the three politicians took a negative tack toward a major IRS investigation targeting users of digital currency exchange Coinbase, writing in the letter:

“[W]e strongly question whether the IRS has actually established a reasonable basis to support the mass production of records for half of a million people, the vast majority of whom appear to not be conducting the volume of transactions needed to report them to the IRS. Based on the information before us, this summons seems overly broad, extremely burdensome, and highly intrusive to a large population of individuals.”

The letter represents the latest wrinkle in the months-long battle by the IRS to obtain user records from the exchange.

The tax agency first went to court in November, seeking to issue a summons for access to Coinbase’s user records. In the most recent development, a group of the startup’s customers – who have requested anonymity – formally asked a US judge in California to intervene and stop the IRS effort in its tracks.

The lawmakers’ official roles also point to the significance of their criticism of the IRS investigation: Hatch chairs the Senate’s Finance Committee, Brady leads the House of Representatives’ Committee on Ways and Means, while Buchanan serves as chair of the House committee’s Oversight Subcommittee.

And others have also previously criticized the IRS approach to digital currencies. Last November, the agency’s own inspector general called for a strategic overhaul, chastising the IRS over its current practices.

Disclosure: CoinDesk is a subsidiary of Digital Currency Group, which has an ownership stake in Coinbase.